Driver assistance system and operating method for a driver assistance system for vehicle longitudinal control

Abstract

Operating method for a driver assistance system (100) for longitudinal vehicle control of a vehicle (1) with respect to a foreign vehicle (2), preferably for speed and / or distance control, wherein the vehicle longitudinal control takes place as a function of at least one current road-specific parameter and / or at least one current vehicle-specific parameter, wherein the operating method comprises the steps: Determining a vehicle class (109) of the other vehicle (2), wherein the vehicle longitudinal control is carried out as a function of at least one parameter derivable from the determined vehicle class (109); and Determining a rear silhouette of the other vehicle (2) driving ahead, on the basis of which the classification of the other vehicle (2) takes place, characterized in that that the operating method is further configured to determine a three-dimensional trajectory of the other vehicle (2) and a three-dimensional trajectory of the own vehicle (1) and to calculate the vehicle longitudinal control as a function of the determined trajectories, wherein a cornering of the other vehicle (2) traveling ahead is determined from a distance to the other vehicle (2) traveling ahead and a changing width and / or a changing height of the silhouette of the other vehicle (2) traveling ahead.

Description

[0001] The invention relates to a driver assistance system for longitudinal control of a vehicle with respect to another vehicle, preferably for speed and / or distance control. The invention further relates to an operating method for a driver assistance system for longitudinal control of a vehicle.

[0002] Regarding the state of the art, reference should first be made to the documents DE 10 2010 028 637 A1, DE 10 2011 118 135 A1, DE 102 58 167 A1, DE 10 2006 023 573 A1, DE 10 2006 036 814 A1 and DE 600 30 240 T2.

[0003] Document DE 10 2010 028 637 A1 describes a method for electronically coupling a first motor vehicle and a second motor vehicle. Information about a vehicle characteristic of the second vehicle is used for the electronic coupling, wherein the vehicle characteristic of the second vehicle influences the resulting air resistance for the first vehicle. For example, this information can indicate the area of the rear view of the second vehicle in the direction of travel.

[0004] Document DE 10 2011 118 135 A1 discloses an adaptive cruise and braking (ACB) control system for controlling a host vehicle following distance. A leading vehicle is detected using a radar sensor and / or a camera sensor. The radar sensor classifies the leading vehicle as a motorcycle, a passenger car, or a commercial vehicle by comparing a detected radar signature with reference radar signatures for different vehicles.

[0005] Document DE 102 58 167 A1 relates to a method for an adaptive cruise control system for a vehicle. The adaptive cruise control system enables the vehicle to maintain a substantially constant speed or to follow a second vehicle in front of the vehicle at a substantially constant distance from the second vehicle.

[0006] Document DE 10 2006 023 573 A1 relates to a method for determining the driving speed of a vehicle, in which a speed signal is generated based on wheel speed detection, the temporal change of the speed signal is determined, and the speed signal is corrected if its temporal change corresponds to a deceleration that is greater than a predetermined deceleration limit. Document DE 10 2006 036 814 A1 shows a system for adaptive cruise control of a vehicle with the steps of calculating the maximum friction coefficient of the road, calculating a minimum safety distance to a vehicle ahead based on the calculated maximum friction coefficient and the current driving speed of a host vehicle.

[0007] Document DE 600 30 240 T2 discloses a method for automatically adjusting a selected following distance for the vehicle based on driving conditions using an adaptive cruise control system for a vehicle, the method comprising: determining a road friction coefficient based on a drive wheel speed of the vehicle and adjusting the selected following distance for the vehicle based on the road friction coefficient.

[0008] For several years now, professional drivers in particular have been burdened with an increasing amount of information about the vehicle's condition, road and environmental conditions, and logistics information while driving. Vehicle manufacturers have responded to this trend by introducing driver assistance systems to relieve the driver's workload. Actively intervening control systems have entered series production for vehicle longitudinal control, which are effective both in non-critical driving situations (in the sense of a risk of accidents) and in critical driving situations.

[0009] An example of a system for longitudinal control in non-critical situations is cruise control with acceleration function and distance control with low deceleration effect (max. approx. -0.3 g). On the other hand, an emergency braking assistant works in critical driving situations to avoid a rear-end collision with high deceleration effect (max. approx. -0.8 g).

[0010] However, such current series systems lack sufficient input of up-to-the-minute driving state and environmental information to ensure consistently effective performance in diverse driving situations. Such systems are therefore inadequately equipped to adapt vehicle longitudinal control to the diverse traffic and driving situations encountered in real-world road traffic. The distance control of such systems is therefore often provided with an additional safety buffer that adjusts the distance between vehicles to a greater distance than actually necessary to prevent a collision from occurring due to unforeseen deviations from the assumptions regarding braking behavior. This, however, leads to inefficient use of traffic space and a lack of acceptance of such systems, particularly when used in commercial vehicles.

[0011] For safety reasons, manual adjustment of the respective control system by the driver can only be performed in non-time-critical situations. Furthermore, the setting selected by the driver may not be the most appropriate for the current driving situation, making manual adjustment prone to errors.

[0012] An object of the invention is to provide a driver assistance system and a corresponding operating method that can better adapt the vehicle longitudinal control to different traffic and driving situations in order to reduce the risk of collision with another vehicle by means of situation-adapted distance control and at the same time enable efficient use of traffic space.

[0013] The objects described above are achieved according to the invention by an operating method for a driver assistance system for vehicle longitudinal control according to claim 1, and by a driver assistance system for vehicle longitudinal control according to claim 11. Preferred embodiments of the invention are described in the dependent claims.

[0014] The operating method according to the invention has the features of independent claim 1.

[0015] In the operating method according to the invention for a driver assistance system for longitudinal vehicle control of a vehicle with respect to another vehicle, the vehicle longitudinal control is carried out as a function of at least one current road-specific parameter and / or at least one current vehicle-specific parameter. The at least one current vehicle-specific parameter can include, for example, a load condition, a condition of the braking system, and / or a tire-specific parameter of the vehicle.

[0016] The term "current" means that the parameter values are determined and continuously updated in real time during vehicle operation, for example, while driving. Vehicle longitudinal control is primarily used for speed and / or distance control.

[0017] In an advantageous embodiment, the current road-specific parameter describes the current condition of the road on which the vehicle is currently traveling, in particular a condition of the road surface or road surface.

[0018] A particularly advantageous road-specific parameter is the road friction coefficient, since differences in the road friction coefficient have a strong influence on the braking deceleration capacity of both the vehicle and the other vehicle and thus significantly influence the required safety distance.

[0019] Furthermore, a predetermined number of road condition classes and / or road friction coefficient classes can be provided, wherein at least one of these classes is selected on the basis of the currently determined road-specific parameter and is taken into account for the vehicle longitudinal control.

[0020] The operating method further comprises the step of determining a vehicle class of a non-vehicle, wherein the vehicle longitudinal control is performed depending on at least one parameter derived from the determined vehicle class. For example, the specific braking deceleration capacity of the vehicle class can be determined depending on the determined vehicle class of the non-vehicle. This has the advantage that the determination of the required safety distance during vehicle longitudinal control can be adapted to the pairing of the vehicle class of the vehicle and the non-vehicle, depending on the situation.

[0021] Particularly precise longitudinal control to the actually required safety distance is made possible if the longitudinal control is dependent on both the current road-specific parameter and the vehicle class of the other vehicle. Thus, the present operating method preferably further comprises adapting a previously known parameter relating to the braking deceleration capacity of the host vehicle as a function of the current road-specific parameter and determining a parameter relating to the braking deceleration capacity of the other vehicle as a function of the determined vehicle class of the other vehicle and the current road-specific parameter. In this case, the vehicle's longitudinal control is dependent on the parameters relating to the braking deceleration capacity of the vehicle and the other vehicle.

[0022] Under unfavorable road friction conditions, especially during precipitation, the comparatively high braking performance of sports cars and motorcycles is significantly reduced due to the road friction coefficient, so that in some cases, the braking performance can even be worse compared to the mass of all vehicles. This results, for example, from extremely wide tires floating due to a lack of rapid water displacement from the tire tread. In such road conditions, a heavy truck can exhibit comparable or even better braking performance than a sports car, so that the safety distance between a truck and a motorcycle traveling ahead can be safely reduced compared to a dry asphalt road, in favor of using the road space.Thus, the actually required safety distance varies greatly depending on the respective vehicle classes of the own vehicle and the other vehicle, taking into account the current road condition, which can be taken into account accordingly in the longitudinal control with the present invention.

[0023] The vehicle classification of the other vehicle is based on determining the rear silhouette of the other vehicle driving ahead. For example, the distance, height, and / or width of the other vehicle can be determined to determine the rear silhouette of the other vehicle. Since different vehicle classes, such as motorcycles, sports cars, cars, or trucks, have different typical heights and / or widths, the vehicle class can be determined based on these dimensions or the resulting rear silhouette, for example, using radar sensors.

[0024] According to an alternative embodiment, vehicle-specific parameters of the other vehicle, such as its class or its braking deceleration capacity, can be received directly from this other vehicle via vehicle-to-vehicle communication, so that the vehicle's longitudinal control is dependent on the received vehicle-specific parameters of the other vehicle. This has the advantage that such parameters do not have to be determined by the vehicle itself, but can be received directly from the other vehicle, avoiding any measurement inaccuracies. However, this requires that both the vehicle and the other vehicle are appropriately configured to send and receive such data. Alternatively, the vehicle could also receive such vehicle-specific parameters of the other vehicle from a stationary transmitting station at the side of the road.

[0025] The accuracy of the vehicle longitudinal control can also be improved by determining one or more current vehicle-specific parameters that influence the vehicle's braking deceleration capability and are incorporated into the vehicle longitudinal control.

[0026] Preferably, a current vehicle-specific parameter includes the vehicle type of the driver's vehicle. The vehicle type of the driver's vehicle is known in advance due to its design and is either permanently configured in the driver assistance system or set once upon commencement of operation.

[0027] Furthermore, the current vehicle-specific parameter can include a loading state. The loading state can be determined as the current weight of the vehicle, the current weight of a trailer, and / or the current weight of a load. In commercial vehicles in particular, the current vehicle weight can vary greatly due to load or people. Since the vehicle-specific braking deceleration capacity depends on the current load, more precise vehicle longitudinal control can be achieved if the vehicle load is currently detected and incorporated into the vehicle longitudinal control. Similarly, the accuracy of the vehicle longitudinal control can be improved if the presence of a trailer is detected and incorporated into the vehicle longitudinal control.

[0028] Furthermore, the current vehicle-specific parameter can also specify whether a trailer is connected or disconnected. Connecting or disconnecting a trailer or semi-trailer results in significant differences in braking (acceleration) performance, so it is advantageous to detect the relevant condition of the entire vehicle and take this into account when setting the safety distance.

[0029] According to a further advantageous embodiment, one or more tire-specific parameters of the vehicle are recorded and incorporated into the longitudinal control. Examples of tire-specific parameters are tire pressure, tire condition, and / or a tire class. Thus, variations in friction between the road surface and the tire caused solely by the tire type or tire class can significantly influence the vehicle's braking performance. Depending on the tire type, summer, winter, all-season, or off-road tires have different friction characteristics between the road surface and the tire. Consequently, improved accuracy can be achieved by additionally considering the tire type as a parameter in the longitudinal control. Similarly, fluctuations in the friction between the road surface and the tire occur for different tire tread depths, particularly during precipitation.

[0030] Furthermore, it is advantageous if the condition of the braking system is also incorporated into the longitudinal control as a vehicle-specific parameter. Both the current load and the maintenance status of the braking system on your vehicle can have a significant impact on your vehicle's braking performance. For example, drum brakes significantly degrade in effectiveness under load due to the sometimes uneven expansion of the cup-shaped drum. Likewise, the effectiveness of the brake pads can decrease due to heat and wear.

[0031] The operating procedure is further configured to determine a three-dimensional trajectory of the other vehicle and a three-dimensional trajectory of the own vehicle and to calculate the vehicle's longitudinal control based on the determined trajectories. By taking into account the three-dimensional trajectories of both the own vehicle and the other vehicle, inclines and declines and the associated changes in the braking deceleration capabilities of both the vehicle and the other vehicle due to the influence of the downhill / uphill lift force can be taken into account. Additionally or alternatively, the road type and the three-dimensional course of the road's trajectory can be determined and incorporated into the longitudinal control.

[0032] The driver assistance system according to the invention for longitudinal control of a vehicle with respect to a third-party vehicle comprises a controller unit configured to carry out the operating method as described above. The previously described aspects of the operating method thus also apply to the controller unit of the driver assistance system.

[0033] Preferred embodiments of the present invention are described in more detail below by way of example and example with reference to the accompanying drawings. Fig. 1 shows a block diagram and illustrates, by way of example, the determined data and calculated functional variables of a driver assistance system according to an embodiment; Fig. 2 shows a table with typical braking deceleration capabilities depending on various road and vehicle-specific parameters according to an embodiment; Fig. 3 illustrates the distance and angle of incidence between the vehicle and the other vehicle as well as the detection of the vehicle class according to an embodiment; Fig. 4 shows a flowchart illustrating a control sequence for a typical driving situation according to an embodiment; Fig. 5A and Fig. 5B schematically illustrate the recognition of the road course based on the change in the vehicle silhouettes according to an embodiment; Fig. 6 shows a flowchart illustrating a control sequence for a further driving situation according to an embodiment; Fig. Figure 7A schematically illustrates the flowchart of Fig. 6 described driving situation; Fig. Figure 7B schematically illustrates a reaction phase that is presented to the driver in the flow chart according to Fig. 6 is granted; Fig. 8 shows a flowchart illustrating a control sequence for a further driving situation according to an embodiment; and Fig. 9 schematically illustrates the driving situation according to the flow chart from Fig. 8.

[0034] The block diagram of the Fig. Figure 1 illustrates the sensors and data 101 used and the functional variables 103 to 112 determined thereby, which can be incorporated into the distance control system. The sensors and data 101 used include the current wheel speed, suspension speed, outside temperature, tire temperature, and axle load. The sensors and data 101 used also include GPS data, navigation data, or data determined using laser sensors, radar sensors, an inclination sensor, an ultrasonic sensor, a camera sensor, or other sensor variables. The aforementioned data and sensors 101 are measured variables and sensors known from the prior art of vehicle technology.

[0035] These recorded data 101 are transmitted via a data connection 102 to a driver assistance system for vehicle longitudinal control 100. Using the transmitted data 101, several functional variables or road- and vehicle-specific parameters 103 to 112 are determined, which are incorporated into the distance control of a control unit 114.

[0036] A functional variable for longitudinal control known from the prior art is the vehicle's own driving speed 103. This can be determined via the wheel speed and / or using GPS data.

[0037] The currently measured shortest distance 104 to the other vehicle 2 and its change can be determined, for example, using radar signals that are reflected from the other vehicle 2. From the own driving speed 103 and the time course of the measured distance to the other vehicle 2, the driving speed 103 of the other vehicle 2 as well as a current braking or acceleration behavior of the other vehicle 2 and the vehicle 1 can be determined. The shortest distance is in Fig. 3 as the length of the arrow 104. If a vehicle 2 is driving straight ahead or slightly offset to the side (upper vehicle in Fig. 3) the distance essentially corresponds to the distance from the front silhouette of vehicle 1 to the center of the rear silhouette of the other vehicle 2. In the case of a other vehicle 2 approaching from the side from behind (lower vehicle in Fig. 3) the shortest distance is essentially determined by the front lateral body section of the other vehicle 2 facing the vehicle 1.

[0038] If the direction of travel between the own vehicle 1 and the other vehicle 2 is not identical, the angle of incidence 105 between vehicle 1 and other vehicle 2 is an important value for the longitudinal control, especially when approaching from the side or when other vehicles 2 are merging. As in Fig. 3, the angle of incidence 105 is the angle between the direction of travel 3 of the vehicle 1 and the distance vector 104 to the other vehicle 2 and can be determined, for example, using a radar sensor 6A. The angle of incidence 105 and the measured shortest distance 104, or their temporal progression, significantly determine the dangerousness and collision risk of the temporal progression of the traffic situation.

[0039] As in Fig. 1, various vehicle parameters 106 of the own vehicle 1 are also determined, which are used to determine the current braking deceleration capacity of the vehicle 1.

[0040] For example, the vehicle type can be recorded. The vehicle type and technical vehicle design are based on a design-related braking (and acceleration) capability. This forms the basis for further calculations for longitudinal control for the respective driving situation. The vehicle type or technical vehicle design is typically already preset in the driver assistance system 100, so it does not need to be newly or continuously determined.

[0041] Other possible current vehicle parameters 106 are based on the current load of vehicle 1 or indicate whether a trailer is attached. The load state can be determined as the current weight of vehicle 1, the current weight of a trailer, and / or the current weight of a load. The total weight is distributed across the axles and can be calculated using their suspension height based on the spring characteristic curve of the suspension struts.

[0042] Additional current vehicle parameters 106 describe the condition of the tires and include several tire-specific parameters of the vehicle 1, such as the tire condition and the tire type with defined or specified tire classes, e.g., summer, winter, all-season, or off-road tires. The tire condition can be recorded as tread depth, for example, as a percentage of the new condition. This also applies to a regrooved tire. Tire wear can be detected from the difference between the vehicle speed calculated from the rolling circumference and the speed recorded via GPS, so that the tire wear is determined automatically and does not have to be entered manually.

[0043] Further possible current vehicle parameters 106 specify the condition of the brake system, for example based on the current maintenance status or the current load status of the brake system 116. The latter, in particular the situational and time-dependent heating of such susceptible brake systems 116, can be detected by local temperature and wear sensors and taken into account accordingly in the vehicle longitudinal control.

[0044] Another class of functional variables that flow into the vehicle's longitudinal control system concerns parameters that describe the current road surface 5. This is how a current road surface condition 107 is determined. The road surface condition 107 can be determined from the direct detection of road surface parameters, such as surface roughness, waviness of the road surface 5, surface temperature of the road surface 5, etc., for example, derived from the work or movement of the spring and damping elements used to stabilize the sprung chassis and body masses of the vehicle 1.

[0045] In addition, ultrasonic sensors can be used to more accurately assess elevation differences in the cross-section of roadway 5. Using corresponding sensor data, the condition of roadway 5 can be classified, for example, using a three-stage classification of roadway 5 into "good," "average," and "poor." The determined roadway condition can then be taken into account when determining the braking deceleration capacity of the host vehicle 1 and the other vehicle 2, for example, via a correction factor or by using corresponding experimentally determined test data.

[0046] Another road surface parameter is the current road friction coefficient (108). This results from both the road surface and the weather conditions. Both influencing factors can be measured using radar sensors, camera systems (including infrared), or laser scanners in logical combination with road structure recognition to perform image comparisons based on a road database and / or data on brightness, echo analysis (strength and scatter of an acoustic reflection), and the outside temperature.

[0047] The data analysis leads to friction coefficient detection with defined or specified friction coefficient classes. Depending on the friction coefficient µF of the road surfaces 5, the following road surface friction coefficient classes are created: µF_1>0.8; µF_2>0.5 to 0.8; µF_3=0.2 to 0.5; µF_4<0.2.

[0048] For further details on determining tire wear, road surface condition and road friction coefficient, please refer to the publication DE 102011 108 110 A1.

[0049] Another functional variable that is included in the vehicle longitudinal control is the vehicle class 109 of the other vehicle 2. Different vehicle classes 109 generally have different braking deceleration capabilities. By determining the vehicle class 109 of the other vehicle 2, the safety distance to the vehicle 2 ahead can be adapted to the current vehicle class 109. For example, cars, but also motorcycles, generally have a significantly higher braking deceleration capability than trucks or buses.

[0050] Fig. Figure 3 illustrates schematically how the class 109 of the preceding vehicle 2 is determined based on the vehicle silhouette. Fig. Figure 3 shows various possible dimensions of rear silhouettes 4A to 4G of a leading vehicle 2. The silhouette designated 4A corresponds to a sports car due to its low height, while silhouette 4B, with a comparable width but greater height, corresponds to a passenger car. The narrower silhouette 4C corresponds to a motorcycle; silhouette 4D, with a similar width to a sports car and passenger car but greater height, corresponds to an SUV. Silhouette 4E corresponds to a van, silhouette 4F to a small truck or city bus, while the largest silhouette 4G corresponds to a truck or coach.

[0051] A predefined number of vehicle classes 109 is stored in the longitudinal controller. Using radar or camera sensors, the height and width of the other vehicle 2 are determined, thus determining the vehicle class 109 of the other vehicle 2 from the predefined number of vehicle classes 109. By taking into account other variables such as the lateral silhouette, the length of the other vehicle 2, and / or the angle of incidence 113, an additional geometry correction can be performed or may become necessary if the recorded heights and widths of the rear silhouette are influenced, for example, by cornering.

[0052] Furthermore, the trajectory 110 of the host vehicle 1 is determined in all three planes. The trajectory 110 of the host vehicle 1 and the trajectory 110 projected to the vehicle 2 in front are calculated to provide precise estimates of the driving situation and the distance to the vehicle 2 in front. The trajectory 110 can be determined, for example, using radar 6, an inclination sensor, and / or GPS data.

[0053] Furthermore, to the extent that the vehicle's own sensors can determine this, the trajectory curve 111 of the vehicle 2 in front is also calculated. This can be done, for example, using radar 6 or laser sensors. For example, cornering can be determined from the distance to the other vehicle 2 in front and the changing width of the rear silhouette of the other vehicle 2, which is recorded using radar or laser data. This is also possible for driving on uphill or downhill gradients. For this purpose, the change in height of the rear silhouette of the other vehicle 2 in front is determined, which is subsequently calculated using the Fig. 5A and Fig. 5B. Instead of determining the trajectory curve 111 of the other vehicle 2 itself, this data can also be received by data transmission from the other vehicle 2 or from a stationary transmitting station (not shown).

[0054] Furthermore, the road type and trajectory 112 of the roads can be determined as a functional variable on three levels. This can be done using the following sub-steps: First, the current road type 112 can be determined from (up-to-date) navigation data. The current road type 112 can include the following values: federal motorway, expressway, federal highway, state road, secondary road, multi-lane urban road, single-lane urban road, main road, secondary road, and, if applicable, construction site. The number of lanes in the direction of travel is then determined taking into account the determined road type 112 and / or from an image comparison with images from a road type database. The road width can then be calculated based on the determined road type 112 and the number of lanes.In order to determine the right and, if applicable, left lane edge, image analysis can be used to determine whether lane markings are present and / or the ground can be scanned (for example using ultrasonic sensors).

[0055] Based on the determined road type 112, the number of lanes, and the calculated road width, a preliminary scan of the roadway 5 is then carried out, for example using radar 6 or laser. The road gradient 5A can then be determined in advance by changing the length of the scanning beam. A gradient 5B of the road can then be determined by sensing the horizon shift through image comparison, taking into account the vehicle pitch or position. If a gradient 5B is detected, the gradient is promptly sensed through at least one of the following steps: sensing the axle load shift (compression travel), decrease in engine tractive power (tractive force diagram), changing the length of the roadway scanning beam, changing the altitude (above sea level) over a longer period of seconds, or changing the GPS position. Using this calculated data, the road's trajectory curve 112 is then calculated in advance.

[0056] The described functional variables 103 to 112 are transmitted via a data connection 113 to a controller unit 114 of the driver assistance system for longitudinal control 100.

[0057] Based on these functional variables 103 to 112, the controller unit 114 determines the current braking deceleration capability of vehicle 1 or of the other vehicle 2 using stored controller tables 200. Based on this braking deceleration capability, the currently required safety distance is then determined, as in known longitudinal control systems. If an adjustment of the safety distance is necessary, the longitudinal controller 114 controls, for example, the brake control 116 of vehicle 1 via an output signal 115.

[0058] Various control tables 200 are stored in the vehicle controller 114, by means of which the current braking deceleration capacity of vehicle 1 and of the other vehicle 2 is determined on the basis of the specific functional variables in order to calculate a current safety distance on this basis. This is done using Fig. 2 is explained in more detail.

[0059] The Fig. Table 200 shown in Figure 2 lists values for typical braking deceleration performance depending on various road and vehicle specific parameters 103 to 112.

[0060] According to the Fig. In the exemplary embodiment described in Figure 2, for determining the braking deceleration capacity of a leading other vehicle 2, a distinction is made between seven different vehicle classes 109 of the other vehicle 2, which are listed in the second row of table 200. For example, the first class includes trucks up to 40 t and high-built coaches. The third row lists the height and width dimensions of the rear vehicle silhouette typical for the respective vehicle class 109. The typical height of such trucks and coaches is between 35 and 40 decimetres and the width is in the range of 23 to 25 decimetres. In a similar way, the height and width dimensions of cars with caravans, SUVs, vans, trucks from 12 to 24 t and buses, sports cars and motorcycles are listed for vehicle classes 2 to 7.

[0061] Table 200 lists typical braking deceleration performance for various vehicle classes 109, assuming a typical driving speed of the other vehicle 2, ABS equipment, suitable tires, and a medium payload. A distinction is made between three road condition classes 107: "good," "medium," and "poor." Furthermore, a distinction is made between four different road friction coefficient classes µF 108, which take into account the different friction coefficient conditions on dry roads, wet roads without standing water, wet roads with standing water or with grippy snow, or roads with slippery snow or ice.

[0062] Each row in the field “Road friction coefficient classes µF” of table 200 indicates the braking deceleration capacity for one of the friction coefficient classes 1 to 4 for the respective vehicle class 109 “1” to “7” of the other vehicle 2, whereby the values in each table field are again differentiated according to the road conditions good / medium / poor.

[0063] By determining the current road surface condition 107 and the current road friction coefficient 108, as in connection with Fig. 1, the currently applicable braking deceleration capacity of the other vehicle 2 driving ahead can thus be determined.

[0064] For example, if the other vehicle 2 driving ahead was identified as a class 2 passenger car, the current road condition 107 was determined to be "good," and the current road friction coefficient µF 108 was > 0.8 (road friction coefficient class "1"), the value 0.95 g for the braking deceleration capacity of the preceding car is taken from the corresponding field of table 200. For a poor road condition 107 (road condition class "poor"), the value would be 0.8 g.

[0065] Under poor road conditions 107 and a road friction coefficient of "3," the braking deceleration would be reduced to 0.35 g. However, if the other vehicle 2 driving ahead under these road conditions is a van (vehicle class 4), the corresponding braking deceleration would be 0.42 g.

[0066] Table 200 illustrates that the braking deceleration capabilities underlying the adaptive cruise control system are highly dependent on the current road surface condition 107 and the current road friction coefficient 108, which can change continuously during a journey. By continuously determining these road surface parameters, the adaptive cruise control system can be continuously adapted to the current road surface condition, so that the adaptive cruise control system is always based on a currently valid braking deceleration capability.

[0067] If the vehicle class 109 of the preceding vehicle 2 is also used as a basis for determining the braking deceleration capacity of the other vehicle 2, the accuracy of the determined braking deceleration capacity can be significantly increased.

[0068] For example, a motorcycle (vehicle class 7, see last column in Table 200) exhibits better braking performance of 1.1 g compared to 0.62 g for a heavy truck in vehicle class "1" under good road conditions 107 and a current road friction class 108 of "1" (dry road) compared to the truck. In contrast, the motorcycle's braking performance deteriorates to 0.12 g under poor road conditions 107 and a current road friction class 108 of "3" (standing water or snow with good grip). That of the heavy truck, on the other hand, deteriorates to only 0.4 g, so that the truck's braking performance is greater than that of the motorcycle under these road conditions. The simultaneous consideration of the current road parameters and the respective vehicle class 109 of the other vehicle 2 thus enables significantly more precise distance control that can adapt to the current driving environment.

[0069] Fig. 2 further illustrates the dependence of the braking deceleration capacity of the host vehicle 1 on vehicle-specific parameters 106 and on road-specific parameters, again distinguishing between the different vehicle classes 1 to 7. Fig. 2 shows only partial exemplary values for individual parameter combinations.

[0070] Column "1" shows the braking deceleration capacity for a passenger car using the values in parentheses for the vehicle-specific parameters vehicle class (passenger car), assumed tire type (all-season tires), tire condition (tread condition of 50% of new condition), load condition (4 people), and brake system condition (factor 1). Only values for an assumed road condition 107 with the value "good" are shown, which is indicated by the selection "x" in the road quality line. For these parameters, the lower four lines of the "possible deceleration" field indicate the vehicle's braking deceleration capacity for the four different road friction coefficient classes 108.

[0071] Similarly, for example, in column “3” or “Van”, the respective braking deceleration capacities for a van as the leading other vehicle 2 with “medium” road surface quality, loaded with one person and braking system factor “1” are given, whereby the values for the braking deceleration capacities are given separately for summer and winter tyres (marked by “S” and “W”).

[0072] Furthermore, it can be seen from Table 200 that in the case of a car which is 100% loaded, whose braking system condition has been assessed with a factor of ‘1’ and which is fitted with summer tyres whose tread condition corresponds to 90% of that of new, the current braking deceleration capacity for a dry road surface of class ‘1’ has the value 0.74.

[0073] It is pointed out that Fig. 2 shows only as an example and in part the braking deceleration capacity stored in the memory of the driver assistance system 100 for a third-party vehicle 2 and the own vehicle 1 for the different value ranges of the determined functional variables 103 to 112.

[0074] So in Fig. 2 does not show that the three-dimensional trajectories and road courses can also be taken into account in the form of additional tables or a correction factor. From the trajectories, the difference between the gradients of the roadway 5A of vehicle 1 and other vehicle 2 can be determined, from which a correction factor can be derived based on the additional slope force in order to adapt the value for the braking deceleration capacity of vehicle 1 and other vehicle 2 to the roadway gradient 5A.

[0075] Based on the braking deceleration capacity of the own vehicle 1 and the other vehicle 2 determined in this way, an exact safety distance can be calculated, taking into account the current driving speed and the angle of incidence 105 of the other vehicle 2, to which the driver assistance system 100 then adjusts.

[0076] The influence of the various functional variables 103 to 112 on braking deceleration performance can be determined by means of test series for different vehicle classes 109. For example, a deterioration in the road surface condition 107 or the road friction coefficient 109 has a negative effect on the braking deceleration performance of the vehicles.

[0077] The determined braking deceleration values for various combinations of road- and vehicle-specific parameters 103 to 112 are then stored as control tables in the vehicle 1, which are accessed by the control unit 114.

[0078] The following figures illustrate the vehicle longitudinal control for some typical driving situations.

[0079] In Fig. 4 describes the control sequence for a driving situation in which a truck semi-trailer 1 follows a sports car 2 (see also Fig. 5). Vehicles 1 and 2 are traveling on a federal highway on dry asphalt and in daylight. The speed of sports car 2 is 80 km / h, as the driver is running in a replacement engine, while semi-trailer truck 1, with a permissible total weight of 40 t, is slowly approaching vehicle 2 in front at 85 km / h.

[0080] In step S400, the other vehicle 2 (the sports car) driving ahead is detected by radar 6. In the next step S401, the distance 104 between the semi-trailer truck 1 and the sports car 2 is determined. Subsequently, in step S402, the vehicle class 109 of the vehicle 2 driving ahead is determined based on the distance 104, the width, and the height of the object. The width and height of the object are detected by radar reflection from the rear silhouette of the vehicle 2 driving ahead. In the present example, the silhouette 4a is recognized and thus identified as the sports car 2.

[0081] Subsequently, in step S403, the angle of incidence 105 to the sports car 2 driving ahead is determined based on the distance 104 and vehicle width. In the present exemplary embodiment, the angle of incidence is <5°, thus the vehicle 2 driving ahead is traveling in the same lane. In step S404, the vehicle's own driving speed 103 is queried, and subsequently, in step S405, the vehicle's own three-dimensional trajectory curve 110 is calculated. In the assumed example, straight-ahead travel on a flat surface is taking place.

[0082] In step S406, the current road type and the road's trajectory curve 112 are calculated. In this example, a federal highway and a straight road are present. Subsequently, in step S407, the road surface condition is calculated, as previously explained. In this example, a level, good road surface 5 is present. In step S408, the road friction coefficient class is determined: the road friction coefficient class µF_1>0.8. Based on this data, the current braking deceleration capacity is determined from the stored characteristic value tables in step S409. Based on the current functional variables, this corresponds to a value of 0.62 g. Subsequently, in step S410, the braking deceleration capacity for other vehicle 2 is determined, which, based on the available functional variables, corresponds to a value of 1.05 g.Based on the determined braking deceleration capacity, the safety distance for the vehicle longitudinal control for a speed of 80 km / h of the preceding vehicle 2 is then calculated in step S411.

[0083] For the calculation of the safety distances and for comparison purposes, the vehicle-typical threshold duration of the braking system 116 until the brake pads are applied and until the further increase in brake pressure until the wheel locking pressure is reached (start of the anti-lock braking system) is also taken into account. Typical guideline values for the vehicle classes passenger car and motorcycle, or truck or semi-trailer are 0.2, 0.3, and 0.7 seconds, respectively. Furthermore, the time it takes the driver to switch from the accelerator to the brake pedal or handle must be taken into account, with an exemplary guideline value being 0.2 seconds; however, this is not relevant for the control system. A guideline value for the safety distance to the vehicle 2 in front as a time gap can then typically be t Sich= 1.8 seconds, but this is not controller-relevant and only serves for comparative calculations. However, the calculation or cycle time of controller 114, which is assumed to be 400 ms, must also be taken into account.

[0084] For a 40 t semi-trailer truck, the brake threshold duration is 0.7 s, plus the calculation time of the controller 114 of 0.4 s, resulting in a total response time t Break for the controller of 1.1 s. From the formula tSich=tBReak+v12*a1−v222*a2*v1 t RBreak = Total response time of driver assistance system 100 and brake 116 a1 = Minimum deceleration of following vehicle 2 a2 = Deceleration of other vehicle ahead 2 v1 = speed 103 following vehicle 2 v2 = speed of other vehicle ahead 2 the safety distance of 41 m is calculated according to a time gap t Sich= 1.85 s. The driver assistance system 100 then regulates the following journey at the calculated safety distance at the same speeds.

[0085] Fig. 5A illustrates how the trajectory curve 111 of the preceding vehicle 2 can be determined based on the changing rear silhouette of the vehicle 2. The rear silhouette of the preceding other vehicle 2 is detected by the vehicle 1 using a radar beam 6. The detected height 7 of the rear silhouette of the other vehicle 2 changes depending on the gradient 5A and gradient 5B of the roadway 5.

[0086] For example, the detected height of the rear silhouette 7 becomes apparently larger when the other vehicle 2 in front enters an incline, compared to the situation where both vehicles 1, 2 are on the same level, so that the rising trajectory curve 111 of the other vehicle 2 in front can be detected by the following vehicle 1 due to the increasing rear silhouette. Similarly, the detectable height of the rear silhouette 7 of the other vehicle 2 in front becomes smaller when the other vehicle 2 in front enters a downhill slope. This is Fig. 5B. In a comparable manner (not shown), right or left turns 111 of the roadway of the other vehicle 2 traveling ahead can be detected by the changing width of the rear silhouette of the other vehicle 2 and dimensionally corrected based on the calculated trajectory.

[0087] Fig. Figure 6 illustrates the control sequence for another typical driving situation. In this example, a truck 1 is traveling in the right lane of a federal highway at a speed of 75 km / h in heavy rain and poor visibility. A foreign vehicle 2 in the form of a truck is approaching from behind on the right, as shown in Fig. 7A, to merge at 85 km / h and thus comes into the radar angle of incidence of truck 1.

[0088] In step S600, the other vehicle 2 approaching from the rear and side is detected by the radar 6. In step S601, the shortest distance 104 to the other vehicle 2 is measured. Then, in step S602, the vehicle class 109 of the approaching vehicle 2 is determined based on the distance and height and identified as a truck or bus. In step S603, the angle of incidence 105 is determined based on the distance 104 from the left front vehicle boundary, which in this example has a value of 150°. Subsequently, in step S604, the vehicle's own driving speed 103 is recorded, which is generally always known. In step S605, the vehicle's own three-dimensional trajectory 110 is calculated, which in the following example corresponds to straight-ahead travel on a flat surface. Subsequently, in step S606, the road type and trajectory 112 of the road are calculated. Based on the assumed driving situation, road type 112 is determined to be a federal highway.Subsequently, in step S607, the road condition 107 is calculated, wherein, according to the assumed driving situation, a good road 5 with a level course is present.

[0089] Subsequently, in step S608, the road friction coefficient class 108 is determined, in this case µF_2 with values from 0.5 to 0.8. In the following step S609, the three-dimensional trajectory 111 of the truck 2 is calculated. In step S610, depending on the determined trajectories 110, 111, it is determined whether a time period or a distance until a possible lateral collision between vehicle 1 and the other vehicle 2 approaching from the side has fallen below a predetermined threshold. If NO, there is no immediate risk of collision and the control sequence goes back to step S600 to further monitor the dangerous situation. However, if a time period or a distance until a possible lateral collision between the host vehicle 1 and the other vehicle 2 has fallen below a predetermined threshold, i.e. a collision could be imminent, a warning signal is output in step S611.In the present example, the risk of a lateral collision or cutting was determined in 3 to 4 seconds and thus an acoustic warning was issued to the driver from the loudspeaker in step S611.

[0090] Subsequently, in step S613, it is determined whether the driver performs a steering and / or braking maneuver, a speed change, or a change in the accelerator pedal during a predetermined reaction phase. For this purpose, the driver can be granted a reaction time of 2 seconds, for example, using a timer to give the driver the opportunity to steer evasively or brake. Such dangerous situations can generally be best resolved by lateral control by the driver, so that the driver is advantageously granted reaction time before the longitudinal control intervenes. Fig. Figure 7B illustrates the reaction phase granted to the driver in step S612 between time t1 and time t2. The length of the reaction phase can be determined depending on the determined time duration of the determined distance until a possible lateral collision.

[0091] If a corresponding driver reaction is detected in step S613, no controller intervention occurs in step S614. However, the vehicle longitudinal control remains in operation to continue monitoring the traffic situation. If the driver does not react within the predetermined reaction time and it is detected in step S615 that a predetermined minimum safety distance is being undercut, the vehicle longitudinal control applies the maximum brake pressure in step S616. Additionally, ABS control is initiated because the friction coefficient is 0.55.

[0092] In step S617, due to the close silhouette of the other vehicle 2 approaching from the side, the other vehicle 2 is detected and classified as a truck. In step S618, braking continues until the safety distance to the classified truck 2 is reached. After the required safety distance is reached, the longitudinal control is terminated in step S619, since the immediate risk of a lateral collision no longer exists and the safety distance has been reached.

[0093] Fig. 8 and Fig. 9 illustrate the longitudinal control for another typical driving situation. As in Fig. As shown in Figure 9, in the present example, a truck 1 follows a leading passenger car 2 along a roadway 5 on a section 5B with a gradient. In the present example, the truck 1 is traveling at a speed of 50 km / h in snowfall and on a snow-covered roadway with poor visibility. As shown in the image below, Fig. As shown in Figure 9, the preceding car 2 then enters a level road. Due to the entry of the preceding car 2 into a level road, its braking deceleration capability improves due to the elimination of the downhill force, so that the safety distance from the following truck 1, which is still on the downhill slope, to this car 2 must be increased.

[0094] In step S800, the gradient of the current roadway 5 is determined. The gradient was determined from the three-dimensional tram curves 112 and / or from the three-dimensional trajectories 110, 111 of vehicle 1 or other vehicle 2. In step S801, the current safety distance on the downhill pass is controlled, taking into account the braking deceleration capabilities of vehicle 1 and other vehicle 2, which were determined as previously using the various function variables 103 to 112. In step S802, an end of the gradient is detected by horizon shift and object changes. The rear silhouette and the visible vehicle front result in a greater object height 7 from the perspective of truck 1.

[0095] In step S803, the vehicle longitudinal control system brakes truck 1 until the distance to the preceding car 2 is adjusted according to the increased braking distance due to the known downhill force. In step S804, the safety distance is readjusted after truck 1 enters the level ground.

[0096] The individual features of the invention are, of course, not limited to the combinations of features described within the framework of the exemplary embodiments presented and can also be used in other combinations depending on the existing vehicle sensor technology. This applies in particular to the combinations of the Fig.1, which can be combined in different ways. For example, only one or more current road-specific parameters can be used to calculate the braking deceleration capacity of the vehicle and the other vehicle. The same applies to the vehicle-specific parameters.

[0097] Furthermore, it is advantageous, but not absolutely necessary, to calculate additional parameters such as determining the vehicle class of the vehicle ahead, the vehicle trajectories, etc. Depending on the selected embodiment, the corresponding adapted control tables for the determined functional variables are then stored in the driver assistance system 100. Furthermore, the number of classes used for the individual parameters, such as vehicle class, road condition class, road friction coefficient class, etc., can of course be adjusted as needed and with the required accuracy. List of reference symbols 1 vehicle 2 third-party vehicles 3 Direction of travel 4A sports car silhouette 4B Car silhouette 4C Motorcycle Silhouette 4D SUV silhouette 4F small truck or city bus silhouette 4G truck or coach silhouette 5 Roadway 5A roadway with gradient 5B Roadway with gradient 6 radar beam 6A radar sensor 7 Height of rear silhouette 100 Driver assistance system for vehicle longitudinal control 101 Sensors and Data 102 Data connection 103 Speed 104 shortest distance to another vehicle 105 angle of incidence 106 vehicle parameters 107 current road conditions 108 current road friction coefficient 109 Vehicle class third-party vehicle 110 3D vehicle trajectory 111 3D trajectory curve of another vehicle 112 Road type and 3D trajectory curve 113 Data line 114 Control unit 115 Control line 116 Brake system 200 Table with road-specific and vehicle-specific braking deceleration capacity

Claims

[1] Operating method for a driver assistance system (100) for longitudinal vehicle control of a vehicle (1) with respect to a foreign vehicle (2), preferably for speed and / or distance control, wherein the vehicle longitudinal control takes place as a function of at least one current road-specific parameter and / or at least one current vehicle-specific parameter, wherein the operating method comprises the steps: Determining a vehicle class (109) of the other vehicle (2), wherein the vehicle longitudinal control is carried out as a function of at least one parameter derivable from the determined vehicle class (109); and Determining a rear silhouette of the other vehicle (2) driving ahead, on the basis of which the other vehicle (2) is classified, characterized by , that the operating method is further configured to determine a three-dimensional trajectory of the other vehicle (2) and a three-dimensional trajectory of the own vehicle (1) and to calculate the vehicle longitudinal control as a function of the determined trajectories, wherein a cornering of the other vehicle (2) traveling ahead is determined from a distance to the other vehicle (2) traveling ahead and a changing width and / or a changing height of the silhouette of the other vehicle (2) traveling ahead. [2] Operating method according to claim 1, wherein the at least one current road-specific parameter describes a current road condition (107) and / or a current road friction coefficient (108). [3] Operating method according to one of the preceding claims, further comprising the steps: Adapting a previously known parameter relating to a braking deceleration capability of the vehicle (1) as a function of the current road-specific parameter; Determining a parameter relating to a braking deceleration capacity of the other vehicle (2) as a function of the specific vehicle class (109) of the other vehicle (2) and the current road-specific parameter, wherein the vehicle longitudinal control is carried out as a function of the parameters relating to the braking deceleration capacity of the vehicle (1) and the other vehicle (2). [4] Operating method according to one of the preceding claims, wherein a distance, a height and / or a width of the other vehicle (2) is determined in order to determine the rear silhouette of the other vehicle (2). [5] Operating method according to one of claims 1 to 3, further comprising the steps: Receiving, from the other vehicle (2), vehicle-specific parameters of the other vehicle (2) and carrying out the vehicle longitudinal control depending on the received other vehicle-specific parameters. [6] Operating method according to one of the preceding claims, wherein the at least one current vehicle-specific parameter comprises at least one vehicle type, a loading condition, a condition of the vehicle braking system and / or a tire-specific parameter. [7] Operating method according to claim 6, wherein the tire-specific parameter describes a tire air pressure, a tire condition, and / or a tire class. [8] Operating method according to claim 6 or 7, wherein the loading condition describes the current weight of the vehicle (1), the current weight of a trailer and / or the current weight of a load. [9] Driver assistance system (100) for longitudinal control of a vehicle (1) with respect to a foreign vehicle (2), preferably for speed and / or distance control, for carrying out the operating method according to one of the preceding claims, characterized by that the driver assistance system (100) comprises: - a provision device designed to provide at least one current road-specific parameter and / or at least one vehicle-specific parameter; and - a control device designed to carry out the vehicle longitudinal control as a function of the at least one current road-specific parameter and / or the at least one vehicle-specific parameter. [10] Commercial vehicle, preferably a truck or bus, with a driver assistance system (100) according to claim 9.

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